土岩组合地铁深基坑施工期变形规律研究

Study of Deformation Law Subway Pit during Construction in for Deep Foundation of Soil and Rock Composite Strata

针对＂土岩组合＂二元地层深基坑相比土质基坑或岩质基坑具有的显著不同的特征,以青岛地铁一期工程＂河西站＂嵌岩桩基坑作为工程研究背景,采用ABAQUS有限元计算和现场大量监测数据分析相结合的方法,对土岩二元地层中地铁深基坑的变形规律展开了研究。研究结果表明：随着开挖深度的增加,围护结构的侧移逐渐增大,侧移的形态基本保持＂鼓胀＂形不变;桩底端水平位移亦随开挖而增大,但侧移较小且增量有限;地表沉降随着开挖深度的增加而增加,且沉降影响范围也随开挖而扩展,紧邻围护结构小范围的土体有少量上抬现象,围护桩处于悬臂状态时地表沉降表现为＂三角形＂模式,基坑顶部架设横向支撑后地表沉降模式转变为＂凹槽型＂;坑底回弹随着开挖深度的增加而增加,回弹主要发生在开挖上部土层的过程中,随着开挖面进入下部岩层,坑底回弹增加趋势放缓。

In respect that the soil rock combination of deep foundation pit has the significantly different characteristics with soil or rock mass foundation pit, in this paper the rock socketed pile foundation pit of Qingdao subway in first phase is taken as the engineering background, ABAQUS finite element calculation and field monitoring data analysis are used to study the deformation law for deep foundation of subway pit during construction in soil and rock composite strata. The research results show that with the increase of excavation depth, palisade structure of lateral increases gradually, lateral basic keep unchanged ＂ballooning＂ form; the shape of the pile bottom also increases with the excavation and horizontal displacement, but smaller lateral and increment is limited; surface subsidence increases with the increase of excavation depth, and the subsidence range extension according to the excavation, close to the retaining structure of a small scale soil lift phenomenon; a small amount of retaining piles are in a slate of cantilever surface subsidence expression is triangle model, the ground settlement after the top mounted horizontal support model into a notch; rebound at pit bottom increases with the increase of excavation depth, and bottom mainly occurs in the proeess of the excavation of upper soil layer, along with the excavation face into the lower strata, rebound at pit bottom increases slow down.